Previously, there were two problems with servlet context initializer
beans that are a scoped proxy:

1. When there's no explicit registration bean the target of the scoped
   proxy is registered rather than the proxy. This meant that the
   proxy had no effect as it was being bypassed.
2. When there is an explicit registration bean, the registration is
   performed twice: the faulty implicit registration described above
   and explicit registration.

A fix (SPR-14816) has been made in Spring Framework so that we can
correctly determine the type of bean that will be produced by a
scoped proxy's factory bean. That change, coupled with the change in
this commit that ignored beans that are the target of a scoped proxy
addresses both of the problems described above. A single registration
is now performed and its the scoped proxy, rather than its target,
that is registered.

Closes gh-7150